Network access mechanism based on power

ABSTRACT

Systems and methods for accessing a contention-based communications network are provided. In systems and methods for accessing a contention-based communications network, an access point in the network is created. The access point is a first node connected to the network configured to receive a request from a second node to gain access to the network. A power of a signal transmitted between the access point and the second node is measured. A probability that the second node will access the network is determined based on the measured power of the signal transmitted between the access point and the second node. A determination of whether to permit the second node to gain access to the network is made based on the determined probability.

CROSS-REFERENCE TO RELATED APPLICATIONS

This disclosure claims priority to U.S. Provisional Patent ApplicationNo. 61/557,321, filed on Nov. 8, 2011, which is incorporated herein byreference.

TECHNICAL FIELD

The technology described in this patent document relates generally tocommunication networks, and more particularly to a contention-basednetwork access mechanism for use in a communication network.

BACKGROUND

Contention-based network access mechanisms are employed in networkcommunication protocols of a variety of different types of communicationnetworks. For example, contention-based network access mechanisms areemployed in local area networks (e.g., Ethernet networks), wirelessnetworks (e.g., wireless networks based on the IEEE 802.11 standard),home area network (HAN) systems, and Advanced Metering Infrastructure(AMI) networks, among others. In a contention-based system, contestantnodes compete for a right or status in a communications network (e.g.,the right to transmit over a shared broadcast medium or a right to joina network of nodes connected to the communications network). Suchcompetition in a contention-based system typically occurs within acontention window, which is a window divided into a number of slots(e.g., 16 or 32) representing communication channels. In a contention,each contestant node selects a communication channel from among theslots of a contention window, and sends a contention participationmessage using the selected communication channel. When severalcontestant nodes are simultaneously attempting to join a network, thecontestant node that selects the lowest slot is determined to have wonthe contention, and a new link in the network is created to connect thewinning node to the network. Once connected to the network, the winningnode and the other connected nodes of the network may share access to acommunications medium via a variety of different protocols (e.g.,Carrier Sense Multiple Access protocol, Time Division Multiple Accessprotocol, and so on).

SUMMARY

The present disclosure is directed to systems and methods for accessinga contention-based communications network. In a method for accessing acontention-based communications network, an access point in the networkis created. The access point is a first node connected to the networkconfigured to receive a request from a second node to gain access to thenetwork. A power of a signal transmitted between the access point andthe second node is measured. A probability that the second node willaccess the network is determined based on the measured power of thesignal transmitted between the access point and the second node. Adetermination of whether to permit the second node to gain access to thenetwork is made based on the determined probability.

In another example, a system for accessing a contention-basedcommunications network includes an access point. The access point is afirst node connected to the network configured to receive a request froma second node to gain access to the network. The system also includesthe second node, which is configured to measure a power of a signaltransmitted between the access point and the second node. The secondnode is also configured to determine a probability that the second nodewill access the network based on the measured power of the signaltransmitted between the access point and the second node. The secondnode is further configured to request access to the network based on thedetermined probability.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram of an example system for accessing acontention-based communications network based on a measurement of apower of a signal transmitted between an access point and a noderequesting access to the network.

FIGS. 2A and 2B are flowcharts illustrating example steps performed byan access point and by a node requesting network access, respectively,for generating a network based on measurements of powers of signalstransmitted between the access point and a plurality of the nodesrequesting network access.

FIGS. 3A, 3B, and 3C illustrate an example network topology built upover time based on measurements of powers of signals transmitted betweenan access point and nodes requesting access to a network.

FIGS. 4A and 4B depict example contention windows having ranges of slotsassigned to nodes based on distances between the nodes and an accesspoint.

FIG. 5 is a block diagram illustrating an example Advance MeteringInfrastructure (AMI) system.

FIG. 6 is a flowchart illustrating a method for accessing acontention-based communications network.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of an example system for accessing acontention-based communications network based on a measurement of apower of a signal transmitted between an access point and a noderequesting access to the network. In FIG. 1, a plurality of nodes 106request access to a communications network 102 through the access point104. The nodes 106 requesting access may represent a variety ofdifferent types of devices. In one example, the communications network102 is the Internet, and the nodes 106 may comprise different wired orwireless devices (e.g., desktop computers, laptop computers, personaldigital assistants, smartphones, cellphones, and other devices equippedto send and receive data over the Internet). In another example, thecommunications network 102 is an Advanced Metering Infrastructure (AMI)network, and the nodes 106 correspond to loads having meters (e.g.,electric meters) and power line communication (PLC) modems configured tosend and receive data over the AMI network. FIG. 1 depicts n nodes 106seeking to gain access to the communications network 102, where n can bea number in the hundreds or thousands, and may thus represent a largenumber of nodes requesting network access.

The access point 104 is connected to the communications network 102 andis used by one or more of the nodes 106 to gain access to the network102. In one example, the access point 104 is a base station device thatconnects wireless device nodes 106 with the network 102 to form awireless network. In another example, the access point 104 is itself anode that previously gained access to the network 102 and is thereafteracting as a central controller configured to provide one or more of thenodes 106 with network access. The access point 104 may utilize acontention-based network access mechanism for granting one or more ofthe nodes 106 access to the network 102.

The determination of how to generate a next link in the network 102(i.e., determining which of the nodes 106 should be given access to thenetwork 102) is based on measurements of powers 110 of signalstransmitted between the access point 104 and each of the nodes 106requesting access to the network 102. The measured powers 110 of thesignals are determined by, among other variables, the distance betweenthe access point 104 and the nodes 106. Although the nodes 106requesting access to the network 102 are depicted in FIG. 1 as beinglocated at equal distances from the access point 104, in examplesystems, certain of the nodes 106 are closer in distance to the accesspoint 104 than others, causing the nodes 106 closer in distance to theaccess point 104 to transmit signals having a relatively higher transmitpower to the access point 104.

The access point 104 may determine which of the nodes 106 should begiven access to the network 102 based on the steps illustrated in FIG.2A. FIG. 2A is a flowchart 200 illustrating example steps performed byan access point for generating a network based on measurements of powersof signals transmitted between the access point and a plurality of nodesrequesting network access. At 202, the access point receives requestsfrom a plurality of nodes 1 . . . n to access a communications network.At 204, the access point measures powers of signals transmitted betweenthe access point and each of the nodes. At 206, using the measuredpowers of the transmitted signals, the access point determines, for eachof the nodes, a probability that the node will be given access to thenetwork. If the access point measures a higher power of a signaltransmitted between the access point and a particular node, theparticular node is determined to have a higher probability of accessingthe network. If the access point measures a lower power of a signaltransmitted between the access point and a particular node, theparticular node is determined to have a lower probability of accessingthe network. At 208, the access point generates a new link in thenetwork between the access point and one or more of the nodes based onthe determined probabilities. A mechanism is used to inform nodes thatthey have been granted access to the network.

In the flowchart 200 of FIG. 2A, the access point determines which ofthe nodes is given access to the network using the measurements of thepowers of the signals transmitted between the access point and thenodes. Under this method, the nodes merely request access to thenetwork, while the access point ultimately controls network access bydetermining the probabilities based on the measurements of the powers ofthe signals transmitted between the access point and the nodes. Inanother example, as illustrated in flowchart 250 of FIG. 2B, theprobability determination based on measurements of powers of signalstransmitted between the access point and the nodes is instead made byeach of the nodes requesting network access (e.g., nodes 106 in theexample of FIG. 1). FIG. 2B illustrates example steps performed by anode for requesting access to a network based on a measurement of apower of a signal transmitted between an access point and the node. At252, the node seeking to access the network measures a power of thesignal transmitted between the access point and the node. At 254, thenode determines a probability of gaining access to the network based onthe measurement of the power of the signal. At 256, the node requestsaccess to the network based on the determined probability. The requestto access the network may be made in the context of a competition, wherea plurality of other nodes are also requesting access to the network. Ifthe node measures a high power of a signal transmitted between theaccess point and the node, the node determines that it has a higherprobability of accessing the network and competes for access based onthis higher probability. If the node measures a low power of a signaltransmitted between the access point and the node, the node determinesthat it has a lower probability of accessing the network and competesfor access based on this lower probability. The competition for networkaccess may be, for example, via a contention-based network accessmechanism.

FIGS. 3A, 3B, and 3C illustrate an example network topology built upover time based on measurements of powers of signals transmitted betweenan access point and nodes requesting access to a network. FIG. 3Aillustrates a network topology 300 at a first point in time. At thefirst point in time, a plurality of nodes are connected to the network302 and a plurality of nodes require access to the network 304. AlthoughFIG. 3A illustrates five nodes requiring access to the network 304, insome examples, the number of nodes requiring access may be in thehundreds or thousands. Due to the finite bandwidth of the network andthe large number of nodes requiring access to the network, not all ofthe nodes 304 can be given access to the network simultaneously. Thus,the nodes requiring access to the network 304 may compete to access thenetwork (e.g., via a contention-based network access mechanism), and newlinks in the network may be generated one-at-a-time to nodes determinedto have won the access competitions.

In one example, a node already connected to the network 302 will, atvarious points in time, provide an opportunity for one or more of thenodes requiring access to the network 304 to join the network. In FIG.3A, connected node 1.3.1 may provide an opportunity for one of the nodesrequiring access to the network 304 to join the network. The connectednode 1.3.1 acts as an access point by receiving requests from othernodes to gain access to the network and generating a new link in thenetwork based on the requests. In determining how to generate the newlink (i.e., determining which of the nodes requiring access to thenetwork 304 should be given access), a system for accessing acommunications network based on measurements of powers of signalstransmitted between the access point and nodes requesting access to thenetwork is utilized. In the system, the connected node 1.3.1 receivesrequests to gain access to the network from the nodes requiring accessto the network 304, and powers of signals transmitted between theconnected node 1.3.1 and each of the requesting nodes 304 are measured.For each of the nodes requiring network access 304, a probability thatthe node will be given network access is determined based on themeasured power of the signal transmitted between the access point andthe node. A new link in the network is generated to one or more of thenodes requiring network access 304 based on the determinedprobabilities.

FIG. 3B illustrates a network topology 350 at a second point in time,after the new link in the network has been generated based on the stepsdescribed above. In FIG. 3B, the new link in the network has beengenerated between the connected node 1.3.1 and node 1, which waspreviously one of the nodes requiring access to the network 304. Thelink in the network to the node 1 is created based on the proximity ofthe node 1 to the access point provided by the connected node 1.3.1. Ascompared to the other nodes requiring network access 304, the node 1 isclosest in distance to the connected node 1.3.1, and thus, the measuredpower of the signal transmitted is highest between the node 1 and theconnected node 1.3.1. Due to the signal transmitted between the node 1and the connected node 1.3.1 having the highest measured power, the node1 is determined to have a high probability of being given access to thenetwork. With the high probability, the node 1 is biased to win anetwork access competition mechanism employed by the connected node1.3.1. The node 1 thus wins the network access competition, causing thenew link in the network to be generated between the connected node 1.3.1and the node 1, as illustrated in FIG. 3B.

FIG. 3C illustrates a network topology 370 at a third point in time.After gaining access to the network, the node 1 may itself create a newlink in the network to another of the nodes requiring access to thenetwork 304. In FIG. 3C, the node 1 has created a new link in thenetwork to a node 3 that was previously one of the nodes requiringaccess to the network. The link in the network to the node 3 is based onthe proximity of the node 3 to the access point provided by the node 1.As compared to the other nodes requiring network access 304, the node 3is closest in distance to the node 1, and thus, a signal transmittedbetween the node 3 and the node 1 has the highest measured power. Due tothe high measured power of this signal, the node 3 is determined to havea high probability of being given access to the network. With the highprobability, the node 3 wins the network access competition, causing thenew link in the network to be generated between the node 1 and the node3, as illustrated in FIG. 3C.

FIGS. 4A and 4B depict example contention windows having ranges of slotsassigned to nodes based on distances between the nodes and an accesspoint. In contention-based network access systems, a plurality ofcontestant nodes compete for a right to join a network. The competitionin contention-based systems occurs via a contention window (e.g.,contention windows 400, 450 of FIGS. 4A and 4B, respectively), which isa window divided into a number of slots representing communicationchannels. In one example, the contention window is opened by an accesspoint in the network (e.g., a base station or a node connected to thenetwork seeking to allow another node to connect to the network). Duringa contention period, each contestant node selects a communicationchannel from among the slots of the contention window and sends acontention participation message using the selected channel. Whenseveral contestant nodes simultaneously attempt to join the network, thecontestant node that selects the lowest slot is determined to have wonthe contention, and a new link in the network is created to connect thewinning node to the network.

FIGS. 4A and 4B illustrate contention windows that operate based onmeasurements of powers of signals transmitted between the access pointand each of the plurality of nodes requiring access to the network. Asdescribed above, communication networks may be accessed based on themeasurements of the powers of signals transmitted between the accesspoint and each of the plurality of nodes requiring access to thenetwork. In accessing networks in this manner, a probability that a nodewill be given access to the network is based on the measured powers ofthe signals, and a new link in the network is generated based on theprobabilities for each of the nodes. In the context of acontention-based network access mechanism, the probability that a nodewill be given access to the network may be determined by assigning tothe node one or more of the numbered slots of the contention window. Theone or more of the numbered slots assigned to the node are the slotsthat the node is able to select during the contention period. Thus, whenselecting a slot of the contention window, a particular node's slotselection choices are constrained based on the determined probabilitythat the node will be given access to the network. Nodes with a higherprobability are assigned lower-numbered slots and thus have a greaterchance of gaining access to the network. Nodes with a lower probabilityare assigned higher-numbered slots and thus have a lower chance ofgaining access to the network.

FIG. 4A illustrates a contention window 400 having a plurality ofnon-overlapping ranges of slots, with each range of slots being reservedfor a particular class of nodes requesting network access. In theexample of FIG. 4A, nodes that are very close to the access point 402can select only slots 0-3. Because the node selecting thelowest-numbered slot of the contention window wins the contention, thenodes that are very close to the access point 402 are biased to win thecontention versus nodes farther away from the access point. Nodes thatare relatively close to the access point 404 can select only slots 4-7,nodes that are far away from the access point 406 can select only slots8-11, and nodes that are very far away from the access point 408 canselect only slots 12-15.

In the example of FIG. 4A, the determination of the proximity of thenodes to the access point is not made based on a physical distancemeasurement but rather based on measurements of powers of signalstransmitted between each of the nodes requesting access to the networkand the access point. Thus, nodes with signals having a higher measuredpower are assigned a lower-numbered range of slots, and nodes withsignals having a lowered measured power are assigned a higher-numberedrange of slots. By assigning to each of the plurality of the nodes oneor more of the numbered slots (i.e., assigning to each node one of theranges of slots 402, 404, 406, 408), the probability that the node willaccess the network is determined based on the measurements of the powersof the signals transmitted between the access point and the nodes. A newlink in the network between the access point and one or more of theplurality of nodes can thereafter be generated based on the determinedprobabilities.

FIG. 4B illustrates a contention window 450 having a plurality ofoverlapping ranges of slots, with each range of slots being reserved fora particular class of nodes requesting network access. In the example ofFIG. 4B, nodes that are very close to the access point 452 can selectonly slots 0-5. By being able to select only the lower-numbered slots0-5, the nodes that are very close to the access point 452 are biased towin the contention versus nodes farther away from the access point.Nodes that are relatively close to the access point 454 can select onlyslots 3-8, nodes that are far away from the access point 456 can selectonly slots 5-12, and nodes that are very far away from the access point458 can select only slots 8-15. The example ranges of slots described inFIGS. 4A and 4B may be modified in various ways (e.g., by defining moreranges or fewer ranges, by changing the sizes of the ranges).

FIG. 5 is a block diagram illustrating an example Advanced MeteringInfrastructure (AMI) system 500. AMI refers to systems that measure,collect, and analyze energy use, and interact with devices such aselectricity meters, gas meters, and water meters through variouscommunication media. AMI systems are capable of collecting detailedenergy usage data on a frequent basis, thus allowing utility companiesto support time-based pricing and demand response programs. A commonchannel access method used in AMI systems is Time Division MultipleAccess (TDMA), where a communications channel is divided intopredetermined time slots that are allocated to certain transmittingnodes exclusively on a repetitive basis. AMI systems may thus includelarge TDMA networks including hundreds or thousands of nodes. Nodesbooting up or having lost connection to the network may be required toacquire network access through a contention-based mechanism. Due to thelarge number of nodes, many contestant nodes may compete to get accessto the network via an existing node in the network that has opened acontention window. New links generated by the node opening thecontention window are characterized by their physical rates (i.e.,megabits per second), which are based on the Signal Noise Ratio (SNR) ofthe links. SNR is proportional to power, and power is dependent ondistance between the newly-connected node and the node opening thecontention window.

FIG. 5, the example AMI system 500 is used in the context of a utilitydistribution system. As shown in FIG. 5, a utility service is deliveredby a utility provider 500 to various loads L₁-L_(n) 502 through adistribution system 504. In one example, the utility service provided iselectric power. Consumption of the utility service by the loads 502 ismeasured at the load locations by meters M₁-M_(n) 506 in the AMI system500, a goal may be to establish transmission paths between each of thenodes and the utility provider 500.

In one example, the meter 506 is a smart meter and includes a Power LineCommunication (PLC) modern used for network communications. The meter506 may be configured to communicate via a network with the loads 502(e.g., via a home area network), and the loads may be, for example,smart appliances. Further, the meter 506 may be configured tocommunicate with the utility provider 500 or any of the other meters 506via an AMI network 510. The communications between the meter 506 and theutility provider 500 over the AMI network 510 may be used for numerouspurposes including scheduling disconnection or connection of utilityservices to the loads 502, automatic meter reading (AMR), smart-gridapplications, and providing additional services such as Internet, video,and audio. The AMI network 510 can be wired, wireless, or a combinationof wired and wireless. The AMI network topology may be built using thepower-based contention mechanism described above.

FIG. 6 is a flowchart 600 illustrating a method for accessing acontention-based communications network. At 602, an access point in thenetwork is created. The access point is a node connected to the networkthat is configured to receive a request from another node to gain accessto the network. At 604, a power of a signal transmitted between theaccess point and a node requesting access to the network is measured. At606, a probability that the node requesting access will be given accessto the network is deter nine based on the measured power of the signaltransmitted between the access point and the node. At 608, adetermination is made as to whether to permit the node to gain access tothe network based on the probability.

While the disclosure has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope of the embodiments. Thus, it isintended that the present disclosure cover the modifications andvariations of this disclosure provided they come within the scope of theappended claims and their equivalents.

It should be understood that as used in the description herein andthroughout the claims that follow, the meaning of “a,” “an,” and “the”includes plural reference unless the context clearly dictates otherwise.Also, as used in the description herein and throughout the claims thatfollow, the meaning of “in” includes “in” and “on” unless the contextclearly dictates otherwise. Further, as used in the description hereinand throughout the claims that follow, the meaning of “each” does notrequire “each and every” unless the context clearly dictates otherwise.Finally, as used in the description herein and throughout the claimsthat follow, the meanings of “and” and “or” include both the conjunctiveand disjunctive and may be used interchangeably unless the contextexpressly dictates otherwise; the phrase “exclusive of” may be used toindicate situations where only the disjunctive meaning may apply.

It is claimed:
 1. A method for providing access to a communicationsnetwork, the method comprising: receiving, by a first node connected tothe network, a signal from a second node that does not have access tothe network and is seeking to gain access to the network; measuring, bythe first node, a power of the signal received from the second node;selecting, by the first node, a group of communication channel slotsbased on the measured power of the received signal, wherein the group ofcommunication channel slots is selected from a plurality of groups ofcommunication channel slots that are respectively assigned to differentpower levels; opening, by the first node, the selected group ofcommunication channel slots for the second node to choose from;selecting, by the second node, one or more of the communication channelslots from the selected group of communication channel slots; anddetermining, by the first node, whether to permit the second node togain access to the network based on (i) the measured power of thereceived signal, and (ii) which one or more communication channel slotsthe second node selected from the group of communication channel slots.2. The method of claim 1, wherein the network is an Advanced MeteringInfrastructure (AMI) network.
 3. The method of claim 1, wherein thedetermining by the first node includes: determining, by the first node,based on the measured power of the signal from the second node, topermit the second node to gain access to the network, and in response tothe determining to permit, the first node opening a communication linkbetween the first node and the second node, through which the first nodeis configured to forward communications between the second node and thenetwork.
 4. The method of claim 3, further comprising: receiving, by thesecond node, a signal from a third node seeking to gain access to thenetwork; measuring, by the second node, a power of the signal receivedfrom the third node; and determining, by the second node, based on themeasured power of the signal from the third node, to permit the thirdnode to gain access to the network; and in response to the determiningby the second node, the second node opening a communication link betweenthe second node and the third node, through which the second node isconfigured to forward communications between the third node and thenetwork.
 5. The method of claim 1, wherein the plurality of groups, fromwhich the selection is made, includes a first group, a second group anda third group, and wherein the second group partially overlaps the firstgroup and partially overlaps the third group.
 6. The method of claim 1,wherein the plurality of groups, from which the selection is made,includes a first group, a second group and a third group that do notoverlap each other.
 7. The method of claim 1, wherein the first nodeperforms the determining such that a probably, of the determiningresulting in permitting the second node to gain access to the network,is positively related to the measured power of the received signal. 8.The method of claim 1, wherein the signal received by the first node isa second signal, and wherein the method further comprises, before thefirst node receives the second signal: receiving, by the second node, afirst signal from the first node; measuring, by the second node, a powerof the first signal; and determining, by the second node, based on themeasured power of the first signal, to transmit the second signal to thefirst node.
 9. The method of claim 8, wherein the second node performsthe determining such that a probably, of the second node determining totransmit the second signal, is positively related to the measured powerof the first signal.
 10. A system, comprising: a network; and a firstnode connected to the network and configured to receive a signal from asecond node that does not have access to the network and is seeking togain access to the network, measure a power of the signal received fromthe second node, select a group of communication channel slots based onthe measured power of the received signal, wherein the group ofcommunication channel slots is selected from a plurality of groups ofcommunication channel slots that are respectively assigned to differentpower levels, open the selected group of communication channel slots forthe second node to choose from, wherein the second node is configured toselect at least one of the communication channel slots from group, anddetermine whether to permit the second node to gain access to thenetwork based on (i) the measured power of the received signal, and (ii)which one or more communication channel slots the second node selectedfrom the group.
 11. The system of claim 10, wherein the network is anAdvanced Metering Infrastructure (AMI) network.
 12. The system of claim10, wherein the determining includes: determining to permit the secondnode to gain access to the network based on the measured power of thesignal from the second node, and in response to the determining topermit, opening a communication link between the first node and thesecond node, through which the first node is configured to forwardcommunications between the second node and the network.
 13. The systemof claim 12, further comprising the second node, wherein the second nodeis configured to: receive a signal from a third node seeking to gainaccess to the network; measure a power of the signal received from thethird node; determine, based on the measured power of the signal fromthe third node, to permit the third node to gain access to the network;and in response to the determining by the second node, open acommunication link between the second node and the third node, throughwhich the second node is configured to forward communications betweenthe third node and the network.
 14. The system of claim 10, wherein theplurality of groups includes a first group, a second group and a thirdgroup, and wherein the second group partially overlaps the first groupand partially overlaps the third group.
 15. The system of claim 10,wherein the plurality of groups includes a first group, a second groupand a third group that do not overlap each other.
 16. The system ofclaim 10, wherein the first node is configured to perform thedetermining such that a probably, of the determining resulting inpermitting the second node to gain access to the network, is positivelyrelated to the measured power of the received signal.
 17. The system ofclaim 10, further comprising the second node, wherein the signalreceived by the first node is a second signal, and wherein the secondnode is further configured to, before the first node receives of thesecond signal: receive a first signal from the first node; measure apower of the first signal; and determine, based on the measured power ofthe first signal, to transmit the second signal to the first node. 18.The system of claim 17, wherein the second node is configured to performthe determining such that a probably, of the second node determining totransmit the second signal, is positively related to the measured powerof the first signal.